Yael Kedar | Tel Hai College (original) (raw)

Papers by Yael Kedar

עוד תוצאות 0 נבחרו עמוד 1 1-10 מתוך 588 תוצאות סימנת 0 תוצאות 1 ספר Theories of colour from Democritus to Descartes / edited by Véronique Decaix and Katerina Ierodiakonou, 2024

Roger Bacon (c. 1220-1292) was one of the earliest commentators on Aristotle's Parva naturalia. I... more Roger Bacon (c. 1220-1292) was one of the earliest commentators on Aristotle's Parva naturalia. In his De sensu commentary, composed in the 1240s, one finds an extensive discussion on the definition and reality of colour. The established division of Bacon's works is in two: the early period of his Paris lectures and the mature period. The later is characterised by an intense occupation with optics, and by the elaboration of his theory of the multiplication of species. Bacon's most thorough discussion of colour is found in his questions on De sensu, which is considered an early work, although it shows marks of a later revision. 1 I present this discussion and its resulting extremely realistic theory of colour in another paper. 2 In this chapter, I examine the ways by which Bacon's interest in optics and the development of the theory of the multiplication of species in his so-called 'mature' writings affected his conception of colour. The most salient feature of his mature interest in colour is the distinction between real and apparent colours, which is the focus of this chapter. This distinction touches the core philosophical conundrum of the validity of sensation in general, and with it, of our ability to properly distinguish between reality and appearance. When cast in the context of our colour experience, the following problem is at stake: do colours inhere in things independently of their relations to light and perceivers, or are they rather a subjective experience? Bacon is firmly grounded within the Aristotelian tradition, which takes colours to have real existence in the world. 3 However, not all colour-experiences are equal, and a demarcation is required between those that can be trusted and those that cannot. This chapter concerns the components of that demarcation, as conceived by Bacon. The chapter begins with a short presentation of the essentials of Bacon's De sensu theory of colour, especially its differentiating criterion between real and apparent colours. It then examines its modifications in his mature period of work. It first addresses Bacon's analysis of the phenomenon of the rainbow and similar phenomena in which a bow of colours appear. Bacon formulates his distinction between real and apparent colours within the frame of this discussion. The influence of the development of his theory of the multiplication of species upon his theory of colour is examined next along with various

Synthese, 2024

In Posterior Analytics 1.13, Aristotle introduced a distinction between two kinds of demonstratio... more In Posterior Analytics 1.13, Aristotle introduced a distinction between two kinds of demonstrations: of the fact (quia), and of the reasoned fact (propter quid). Both demonstrations take a syllogistic form, in which the middle term links either two facts (in the case of quia demonstrations) or a proximate cause and a fact (in the case of propter quid demonstrations). While Aristotle stated that all the terms of one demonstration must be taken from within the same subject matter, he admitted some exceptions in which the fact and the reasoned fact are instantiated by terms from different sciences, as when mathematics provides the reason and another science the empirical fact. This was the methodological foundation of the “mixed sciences”, a subject of varying interpretations in the thirteenth century. Roger Bacon (C. 1220–1292), adhering to Robert Grosseteste’s (C. 1168–1253) commentary on Posterior Analytics, presented a unique interpretation of this exception. He replaced propositional demonstrations with geometrical considerations and diagrams, thus producing geometrical arguments for theorems in natural philosophy. I focus on Bacon’s propter quid arguments, as applied in three case studies: (1) the heat caused by a body moving to its natural place; (2) the motion of the scale; (3) and the contraction of water. Based on an analysis of these demonstrations, I argue that Bacon’s interpretation of propter quid demonstration reflects his application of a scientific methodology that imbues geometrical objects with causal power over material bodies.

British journal for the history of philosophy, May 29, 2024

The paper argues that Roger Bacon adhered to a unique form of geometrical atomism, according to w... more The paper argues that Roger Bacon adhered to a unique form of geometrical atomism, according to which elemental matter can be analysed into cubic (when at rest) or pyramidal (when in motion) portions. Bacon addressed geometrical atomism from the perspective of the Aristotelian review, using his interpretation of Aristotelian principles to render the theory plausible. He was mostly concerned with solving the contradiction between the angular shapes of the portions and the shape of the elemental spheres. His motivation for doing so, I argue, was his conviction in the applicability of geometry onto natural philosophy, and his goal was to render matter capable of geometrical analysis. In this way, he was convinced, geometrical properties can be considered efficient causes of matter’s spatial formation and motion.

BJHP, 2024

The paper argues that Roger Bacon adhered to a unique form of geometrical atomism, according to w... more The paper argues that Roger Bacon adhered to a unique form of geometrical
atomism, according to which elemental matter can be analysed into cubic
(when at rest) or pyramidal (when in motion) portions. Bacon addressed
geometrical atomism from the perspective of the Aristotelian review, using
his interpretation of Aristotelian principles to render the theory plausible. He
was mostly concerned with solving the contradiction between the angular
shapes of the portions and the shape of the elemental spheres. His
motivation for doing so, I argue, was his conviction in the applicability of
geometry onto natural philosophy, and his goal was to render matter
capable of geometrical analysis. In this way, he was convinced, geometrical
properties can be considered efficient causes of matter’s spatial formation
and motion.

In Posterior Analytics 1.13, Aristotle introduced a distinction between two kinds of demonstratio... more In Posterior Analytics 1.13, Aristotle introduced a distinction between two kinds of demonstrations: of the fact (quia), and of the reasoned fact (propter quid). Both demonstrations take a syllogistic form, in which the middle term links either two facts (in the case of quia demonstrations) or a proximate cause and a fact (in the case of propter quid demonstrations).
While Aristotle stated that all the terms of one demonstration must be taken from within the same subject matter, he admitted some exceptions in which the fact and the reasoned fact are instantiated by terms from different sciences, as when mathematics provides the reason and another science the empirical fact. This was the methodological foundation of the “mixed sciences”, a subject of varying interpretations in the thirteenth century. Roger Bacon (C. 1220–1292), adhering to Robert Grosseteste’s (C. 1168–1253) commentary on Posterior Analytics, presented a unique interpretation of this exception. He replaced propositional demonstrations with geometrical considerations and diagrams, thus producing geometrical arguments for theorems in natural philosophy. I focus on Bacon’s propter quid arguments, as applied in three case studies: (1) the heat caused by a body moving to its natural place; (2) the motion of the scale; (3) and the contraction of water. Based on an analysis of these demonstrations, I argue that Bacon’s interpretation of propter quid demonstration reflects his application of a scientific methodology that imbues geometrical objects with causal power over material bodies.

Encyclopedia of Medieval Philosophy, 2018

Robert Grosseteste and the pursuit of Religious and Scientific Learning in the Middle Ages, 2016

I claim that Grosseteste and Bacon played a crucial role in the evolution of the idea that nature... more I claim that Grosseteste and Bacon played a crucial role in the evolution of the idea that nature is governed by laws. The idea that the explanatory terms of natural phenomena are universal, necessary and impersonal laws which can be formulated quantitatively, replaced the Aristotelian emphasis on the ‘nature’ or the ‘form’ of a thing. The Aristotelian explanation placed individual objects and phenomena at the center of attention and considered their cause of change internal, namely, the aspiration to realize potentialities.

Annals of Science, 2015

The paper examines the relevance of the nomological view of nature to three discussions of tide i... more The paper examines the relevance of the nomological view of nature to three discussions of tide in the thirteenth century. A nomological conception of nature assumes that the basic explanatory units of natural phenomena are universally binding rules stated in quantitative terms. (1) Robert Grosseteste introduced an account of the tide based on the mechanism of rarefaction and condensation, stimulated by the Moon's rays and their angle of incidence. He considered the Moon's action over the sea an example of the general efficient causality exerted through the universal activity of light or species. (2) Albert the Great posited a plurality of causes which cannot be reduced to a single cause. The connaturality of the Moon and the water is the only principle of explanation which he considered universal. Connaturality, however, renders neither formulation nor quantification possible. While Albert stressed the variety of causes of the tide, (3) Roger Bacon emphasized regularity and reduced the various causes producing tides into forces. He replaced the terminology of 'natures' by one of 'forces'. Force, which in principle can be accurately described and measured, thus becomes a commensurable aspect of a diverse cosmos. When they reasoned why waters return to their place after the tide, Grosseteste argued that waters return in order to prevent a vacuum, Albert claimed that waters 'follow their own nature', while Bacon held that the 'proper force' of the water prevails over the distant force of the first heaven. I exhibit, for the thirteenth century, moments of the move away from the Aristotelian concerns. The basic elements of these concerns were essences and natures which reflect specific phenomena and did not allow for an image of nature as a unified system. In the new perspective of the thirteenth century the key was a causal link between the position of the Moon and the tide cycle, a link which is universal and still qualitative, yet expressed as susceptible to quantification.

Studies in History and Philosophy of Science Part A, 2006

Plotinus resolved the paradox of the immanent transcendence, characterizing the relation between ... more Plotinus resolved the paradox of the immanent transcendence, characterizing the relation between the One and the universe, through his theory of the two energeiai. According to this doctrine, all existents have an internal activity and an external activity: the internal activity comprises the true essence and substance of each being; the external activity is emitted outwards as its image. The source of the emission is thus present in the lower layer of being by virtue of its manifold images. The prominence given to light in elucidating this solution led to a distinction between two types of lights: an original light, corresponding to the internal energeia of every existent, and a secondary light, which is the outflow and image of the first light, existing outside of the luminous body. This paper demonstrates the striking similarity between these two Plotinian lights and the concepts of lux and lumen developed by two thirteenth-century philosophers: Robert Grosseteste and Albertus Magnus. Moreover, the paper contends that the purpose of these two medieval concepts of light was identical to what Plotinus had in mind when he first made the distinction: to account for the relation between the one and the many.

Early Science and Medicine, 2009

In this paper I challenge the claim that Bacon considered the operation of species as limited to ... more In this paper I challenge the claim that Bacon considered the operation of species as limited to the physical and sensory levels and demonstrate that in his view, the very same species issued by physical objects operate within the intellect as well. I argue that in Bacon the concept of illumination plays a secondary role in the acquisition of knowledge, and that he regarded innate knowledge as dispositional and confused. What was left as the main channel through which knowledge is gained were species received through the senses. I argue that according to Bacon these species, representing their agents in essence, definition and operation, arrive in the intellect without undergoing a complete abstraction from matter and while still retaining the character of agents acting naturally. In this way Bacon sets the intellect as separate from the natural world not in any essential way, but rather as it were in degree, thus supplying a theoretical justification for the ability to access and k...

Revista Española de Filosofía Medieval

The paper examines Roger Bacon’s use of the concept virtus in the Communia naturalium and De mult... more The paper examines Roger Bacon’s use of the concept virtus in the Communia naturalium and De multiplication specierum. It focuses on the roles which virtus and species play as vehicles of causality in the inanimate realm. It analyses the distinct functions played by virtus in the motion of celestial spheres, the power of natural place, the attraction of iron to magnet, and the universal nature. The analysis concludes that virtus is an efficient power, a feature of form, capable of causing local motion and instigating natural processes. Species is matter’s response to the stimulation made by virtus through which every natural action, to the exclusion of local motion, is made. Species is a non-efficient power, an ‘appetite’ internal to matter. It is an expression of matter’s inherent inclination to promote and perfect itself, the result of matter’s ‘active potentiality’.

Revista Española de Filosofía Medieval

Journal of the History of Philosophy, 2020

Studies in History and Philosophy of Science Part A, 2020

Perspectives on Science, 2017

Bacon discussed three different types of laws of nature: (1) particular laws governing one elemen... more Bacon discussed three different types of laws of nature: (1) particular laws governing one element or phenomenon (such as the law of the gravity of water); (2) the laws of the multiplication of species; and, (3) the universal law of nature. Each set of laws has its own explanatory function: (1) the particular laws account for the unique features of individuals and species; (2) the laws of multiplication explain the common features of matter and how individuals affect one another physically; and (3) the law of universal nature regulates these interactions and keep them in balance. Bacon’s laws share common features with early modern conception of laws. For example, they can be restated as if/then sentences and cover future events; some support counterfactuals; and all are endowed with explanatory power and free from space-time limitations. When considered together, they form a system, ordered in hierarchical relations. The different levels of laws cover three aspects of Aristotelian causality: formal, efficient, and final. The law of universal nature is a metaphysical axiom, necessary for upholding the very idea of a nature governed by laws. This indicates that Bacon conceived of nature as orderly and predictable; he presented a conception of a lawful nature and showed an understanding of what it takes to be lawful to a degree that had not been seen before.

Revista Española de Filosofía Medieval:, 2021

its main tenets through the writings of other thinkers, such as Avicenna and al-Farabi. The end r... more its main tenets through the writings of other thinkers, such as Avicenna and al-Farabi. The end result of this attempt is a sketch of a political theory that goes mainly under the name of Aristotle but has little to do with the actual contents of the Politics. It is a very good index, however, of the breadth and depth of medieval accounts of social, political and moral life. Important here is the understanding of scientia civilis-moralis. Lambertini presents Bacon's important introduction to his Moralis philosophia (= Opus maius, Part VII) and then provides a very helpful analysis of Part II, the section on social and political life based on Avicenna's Metaphysics X, Parts IV and V. A focal point is the central role of the law and the lawgiver in Jewish, Muslim and Christian approaches to social and political life. The lawgiver must be more than a practical lawyer: he must know the moral foundations of the law. This becomes very important in the context of an account of the different religions of the world such as Bacon presents in Moralis philosophia, Part IV. The De scientiis of al-Farabi is a major source of Bacon's concept of Aristotle's Politics. Or rather, it enabled Bacon to think of what the latter text might be. The final section based on the Opus tertium and the Compendium studii philosophiae presents Bacon's well-known critique of the lay lawyers influenced by the civil law and canon law emanating from Bologna. For Bacon, the lawgiver needed to know the philosophical foundation found in the moral teaching of Aristotle and the theological foundations of the law as found in the sacred Scripture. Jeremiah Hackett's "Roger Bacon's New Metaphysics (1260-1292): The Integration of Language Study and Natural Science with Metaphysics and Morals" presents a synthesis of the many strands of Bacon's philosophical doctrines concerning the person. It begins with a review of Bacon's concept of method in his metaphysics. It proceeds to identify Bacon's tasks in the Franciscan house of studies at Paris, that is as one who did critical work on the Hebrew, Greek and Latin texts of sacred Scripture. Hackett then takes up Ferdinand M. Delorme's argument that at some time in the 1260s Bacon wrote a new work on metaphysics. Using wider information from the Communia mathematica and crossrelating it to the Opus maius, Hackett argues that the Opus maius, as the sketch for an Opus principale, or a Summa sapientiale, was designated by Bacon as his new work in metaphysics. Hackett outlines an account of the structure and sources of this new metaphysics conceived by Bacon. From the point of view of scientific method, two authors are prominent: Ptolemy in his Optics and especially his Almagest, and Augustine in his De musica, Book 6, on number, measurement, and vision. Next, the philosophical sources for Bacon's new metaphysics are examined, with close connection to morals as given in Moralis philosophia, Part I. Important here are Aristotelian and Stoic sources, but even more so are the various Platonic and Neoplatonic texts. The central role of perspectiva for Bacon's understanding of knowledge and the human being is accentuated. Against some modern authors who impute an Avicennian substance dualism to Bacon and other thirteenth-century English Franciscans, Bacon's doctrine of the unity of the human being is defended. The metaphysical portrait of the human being depicted by Bacon is that of a living bodily perspectivus whose intellect and cogitative power function as a unity. In the end, Bacon's new metaphysics finds its fulfilment in a metaphysical anthropology which

Synthese, 2024

British journal for the history of philosophy, May 29, 2024

BJHP, 2024

The paper argues that Roger Bacon adhered to a unique form of geometrical atomism, according to w... more The paper argues that Roger Bacon adhered to a unique form of geometrical
atomism, according to which elemental matter can be analysed into cubic
(when at rest) or pyramidal (when in motion) portions. Bacon addressed
geometrical atomism from the perspective of the Aristotelian review, using
his interpretation of Aristotelian principles to render the theory plausible. He
was mostly concerned with solving the contradiction between the angular
shapes of the portions and the shape of the elemental spheres. His
motivation for doing so, I argue, was his conviction in the applicability of
geometry onto natural philosophy, and his goal was to render matter
capable of geometrical analysis. In this way, he was convinced, geometrical
properties can be considered efficient causes of matter’s spatial formation
and motion.

In Posterior Analytics 1.13, Aristotle introduced a distinction between two kinds of demonstratio... more In Posterior Analytics 1.13, Aristotle introduced a distinction between two kinds of demonstrations: of the fact (quia), and of the reasoned fact (propter quid). Both demonstrations take a syllogistic form, in which the middle term links either two facts (in the case of quia demonstrations) or a proximate cause and a fact (in the case of propter quid demonstrations).
While Aristotle stated that all the terms of one demonstration must be taken from within the same subject matter, he admitted some exceptions in which the fact and the reasoned fact are instantiated by terms from different sciences, as when mathematics provides the reason and another science the empirical fact. This was the methodological foundation of the “mixed sciences”, a subject of varying interpretations in the thirteenth century. Roger Bacon (C. 1220–1292), adhering to Robert Grosseteste’s (C. 1168–1253) commentary on Posterior Analytics, presented a unique interpretation of this exception. He replaced propositional demonstrations with geometrical considerations and diagrams, thus producing geometrical arguments for theorems in natural philosophy. I focus on Bacon’s propter quid arguments, as applied in three case studies: (1) the heat caused by a body moving to its natural place; (2) the motion of the scale; (3) and the contraction of water. Based on an analysis of these demonstrations, I argue that Bacon’s interpretation of propter quid demonstration reflects his application of a scientific methodology that imbues geometrical objects with causal power over material bodies.

Encyclopedia of Medieval Philosophy, 2018

Robert Grosseteste and the pursuit of Religious and Scientific Learning in the Middle Ages, 2016

Annals of Science, 2015

Studies in History and Philosophy of Science Part A, 2006

Early Science and Medicine, 2009

Revista Española de Filosofía Medieval

Journal of the History of Philosophy, 2020

Studies in History and Philosophy of Science Part A, 2020

Perspectives on Science, 2017

Revista Española de Filosofía Medieval:, 2021

Premodern Nature: Regularity, Exceptions, Manipulations, 2019

Premodern science considered nature through Aristotle’s definition of an intrinsic principle, dri... more Premodern science considered nature through Aristotle’s definition of an intrinsic principle, driving species and individuals towards perfection, in a less or more regular manner which allows scientific knowledge. However, sometimes things go wrong—nature incidentally makes mistakes. Can natural errors (like “monsters”) be amended?
This panel addresses the tensions between regularity and exceptions, description and manipulation of nature in premodern times. How did premodern thinkers justify the exceptions to the regularity of nature? What were the conditions for their assumption that an exception to that regularity was “unnatural”? How did they think they could achieve a manipulation of nature? By “manipulation” we mean the propelling of natural regulated changes towards a preconceived goal. Which presuppositions enabled them to consider the possibility of such manipulation? What was the metaphysical, epistemological, and theological frame that supported this kind of thinking?
Nicholas Aubin explores the relation between nature, art, and medicine in the Muslim tradition as expressed in al-ʿĀmirī’s thought. Marienza Benedetto addresses the birth of monsters in the Jewish tradition, as found in Maimonides medical works. Nicola Polloni examines patterns of regularity and irregularity of nature in Hermann of Carinthia of the Latin-Neoplatonist tradition. The Latin-Aristotelian tradition of the manipulation of nature is investigated by two papers, both focused on Roger Bacon. Yael Kedar speaks about Bacon’s conception of natural legality, and asks whether this new conception fostered ideas of controlling nature, and Jeremiah Hackett investigates the theological aspect of Bacon’s “experimental science”.

Religions and Interreligious Dialogue in the Galilee is a theoretical and experiential course des... more Religions and Interreligious Dialogue in the Galilee is a theoretical and experiential course designed to give students a deeper understanding of the historical, political, and religious background of Galilee communities, and to experience interreligious dialogue. The course takes advantage of our unique setting to supplement lectures and panel discussions with on-site learning, meeting with leaders and exploring religious sites of the diverse Christian, Jewish, Muslim, and Druze communities. The course will focus on conflict resolution and interreligious dialogue from religious leaders and activists for whom these challenges are part of their daily life. Eligibility The course is open to a limited number of participants. Graduate students, postdocs and research scientists from institutions of higher education of all nationalities are welcome to attend. * The course will be taught in English.

The Philosophy and Science of Roger Bacon. Studies in Honour of Jeremiah Hackett Edited by Nicola Polloni and Yael Kedar. London: Routledge, 2021. 270 pp. ISBN: 9780367471743., 2021

Physics De sensu et sensato De generatione et corruptione De animalibus De anima De caelo et mund... more Physics De sensu et sensato De generatione et corruptione De animalibus De anima De caelo et mundo De causis De plantis libri naturales Sentences De mirabilis potestate